Shading Plants from the Summer Heat

Summer can bring on some extreme heat — upper 90s to well over 100° in some areas. Add to that humidity and strong sun in the southern and southwestern regions of the county, and you’ve got a recipe for heat stress in the garden (not to mention in the gardener!). Here’s what you need to know about how to protect your plants when the heat is on, and how to stay strong trying to combat the hottest months of the year.

How Do I Know if My Plants Need Extra Shade?

First, it’s important to remember that most young transplants, particularly when planted in the heat of the summer, could use some added protection until they get established. Similarly, your older plants may develop heat stress more easily because they may be on the end of their lifecycle and more prone to damage, disease, or pests.

Aside from the age of your plants, watch out for these signs of heat stress:

• Sunburned foliage and fruits: Look at the skin or edges of your plants and fruits — do you see yellowing and crisping? It’s probably heat-related.
• Blossom end rot: This is most frequently seen in veggies like tomatoes — the blossom end of the fruit softens and rots, and it’s a major irritation to many gardeners. While there are several causes of it, one of them is drought stress and soil moisture fluctuations brought on by heat.
• Blossom drop: Before the plant can produce the fruit, it has a blossom, and that blossom can drop right off in the presence of high heat.
• Wilting: While wilting is normal in warm temps, what’s not normal is continual wilting, even after watering or when the sun is down.
• Leaf drop: When plants get too heat stressed, they’ll simply drop their leaves because they can’t uptake water fast enough from the soil to offset the high heat.

Ways to Shade

1. Shade Cloth: Shade cloth is a lightweight fabric that has tiny holes to allow sunlight and water to permeate, and it helps block some of the intense sun that occurs during periods of high heat. Use shade cloth over garden hoops to protect long garden rows, or install “shade sails” to create your own custom shade environment.
2. Row Covers: Row covers are similar to shade cloth and can be draped over the garden hoops (above) or laid down loosely over the tops of young plants. This has the added benefit of excluding pests that normally love to feast upon your young transplants, causing all manner of damage. Use lightweight row covers to shade your plants — and if you opt for a medium-to-heavy weight row cover, remember to partially lift it on very hot days inorder to ensure proper air circulation. Your row cover product should clearly display the weight of the material — heavyweight weighs 2 oz. per square yard, medium weight weighs 1 ¼ oz. per square yard, and lightweight weighs ½ oz. per square yard.
3. Larger Plants: One of the easiest (and free!) ways to shade your plants is to use the existing, larger plants you have on hand.For example, if you have long squash vines growing up a tunnel trellis, it’ll cast shade on the soil directly below it — so take advantage of that area to plant your younger veggies that need a little protection. It’ll still be bright light but, depending upon the angle of the sun, not direct sun all day long. Want to plan ahead?Try a “3 Sisters Garden” with squash, beans, and corn — as the plants grow, the squash leaves provide shade to the soil and the plants below. Don’t know how to plant a 3 Sisters Garden? Learn how here: 6 Steps on How to Plant a 3 Sister Garden

Once you have shading down to a science, you might consider adding in some shade loving Perennials to come back year after year.

What Should I Grow?

While many perennials grow well in a wide variety of USDA Hardiness Zones, you’ll want to seek advice from your local trusted garden center for the varieties that work best for your particular area. Still unsure? Check out our Top 5 Perennials for Shade and see if one — or all — work for you.

1. Ajuga (Ajuga spp.): This tiny groundcover does its magic close to the ground — 6” above it, to be exact. It’s hardy from zones 3-9, and in warmer climates, it’s often evergreen. Leaves are dark purple, green, or variegated with blue, pink, or white flowers. Look for ‘Black Scallop,’ ‘Golden Glow,’ ‘Bronze Beauty,’ or my favorite, ‘Chocolate Chip.’
2. Hosta (Hosta spp.): Hostas, also known as plantain lily, is one of the shining stars of the shade garden. Its clumping habit, rounded or almost heart-shaped leaves, and lush growth makes them a gardener’s favorite. Leaves are blue, green, gold, white, or chartreuse — many with variegated markings. Hardy from zones 3-8, hostas grow anywhere from 6” across to several feet in diameter. ‘Blue Mouse Ears,’ ‘Stained Glass,’ and ‘Pandora’s Box’ are stunning varieties to try.
3. Hellebore (Helleborus spp.): Also called Lenten Rose, hellebores grow up to 12” tall from zones 4-9. One of the earliest of the perennials to poke its head out in late winter or early spring, hellebores have gold, green, or chartreuse foliage with cup-shaped flowers in tones of burgundy, pink, white, or green. ‘Royal Heritage,’ ‘Ivory Prince,’ ‘Apricot Blush,’ and ‘Ruse Black’ are particularly beautiful.
   Astilbe (Astilbe spp.): Astilbe, or False Spirea, grows up to 4’ tall depending on variety, and features fine foliage with fluffy, plumelike flowers in shades ranging from white to burgundy. This early summer bloomer is happy in zones 4-9, and handles dappled morning sun like a pro. Look for ‘Fanal,’ ‘Deutschland,’ ‘Sprite,’ and ‘Purple Blaze.’
4. Lilyturf (Liriope spicata): Lilyturf, or liriope, is a valuable groundcover prized for its strappy foliage in tones of green, white, and silver. Added benefits are blue or white flowers, dark berries in autuman, and deer and rabbit resistance. Liriope grows up to 12” tall in zones 5-10, being evergreen in milder climates. Try ‘Majestic,’ ‘Silver Dragon,’ ‘Lilac Beauty,’ or ‘Variegata.